commit 68c4e639587090389147c06cf271308b058ef288
Author: Stu Hood <stuhood@gmail.com>
Date:   Sat May 9 20:59:17 2015 -0700

    Replace custom softreference cache with a guava cache.
    
    The cache for analysis shows up as highly contended after the other analysis fixes. This replaces the custom cache with a guava softreference cache, which defaults to being striped for 4 writers, and which allows concurrent reads.
    
    Testing Done:
    org.pantsbuild;zinc#1.0.1:
      main:compile:jvm:jvm-compilers:compile:zinc: 448.450177431
    this patch:
      main:compile:jvm:jvm-compilers:compile:zinc: 412.523220778
    
    Reviewed at https://rbcommons.com/s/twitter/r/2190/

 src/scala/org/pantsbuild/zinc/Cache.scala    | 93 ++++++----------------------
 src/scala/org/pantsbuild/zinc/Compiler.scala | 15 +++--
 src/scala/org/pantsbuild/zinc/Nailgun.scala  |  2 +
 3 files changed, 32 insertions(+), 78 deletions(-)